No surprise everyone is talking about distillers’ dried grains with solubles and looking for ways to include them in swine rations.

The pros, cons and usage rates are still being sorted out and probably will be for some time. But there is another consideration in using and handling DDGS that can present some challenges — poor flowability. While it’s not a problem across the board, there are certain conditions that enhance the issue.

The flowability and bridging challenges most often occur in bulk storage containers and transport vehicles. Bottom line, this can limit the ability to use DDGS.

“Few attempts to characterize factors affecting flowability of DDGS have been reported in controlled studies,” says Lee Johnston, swine nutritionist at University of Minnesota’s West Central Research and Outreach Center, Morris, Minn.

He points to calcium carbonate, which is routinely added to soybean meal to improve the flow. “We theorized that addition of flow agents to DDGS might improve flowability,” Johnston notes. So a University of Minnesota swine research group designed a study to determine whether adding selected agents would improve DDGS flowability in practical commercial conditions.

The study, funded by the Minnesota Pork Board, was conducted at the BushMills Ethanol plant in Atwater, Minn., and involved four treatments. These included:

  • A control, which received no flow agent
  • 5 pounds per ton of DMX-7
  • 2 percent calcium carbonate
  • 1.25 percent of a clinoptilolite zeolite. 

Each of the agents was mixed into 5,000-pound lots of DDGS that contained 9 percent or 12 percent moisture, which provided eight total treatments.

“Once the DDGS lots were prepared, we loaded each one into a separate compartment of a commercial feed truck,” Johnston notes. The truck then traveled about 150 miles, sat idle for two days, and traveled 150 miles back to the ethanol plant.

“Upon returning to the plant, we recorded the time required to unload each truck compartment,” he adds. “The time, combined with the known weight of DDGS loaded into the compartment, allowed us to calculate a flow rate (pounds per minute) for each treatment.”

Then the research team repeated the procedure. “The first thing we noticed quite convincingly in the data was that drying DDGS to 9 percent moisture greatly improved flowability compared to 12 percent moisture,” Johnston relates. “The drier product unloaded at 1,368 pounds per minute while the wetter DDGS flowed at 859 pounds per minute. We expected this result from our previous experiences and reports from the feed industry.”

However, researchers found that none of the agents tested significantly improved the DDGS flow rate compared with the control treatment, which included no additive. That was true regardless of whether the DDGS moisture levels were 9 percent or 12 percent. The control’s flow rate was 1,123 pounds per minute; the treatments with flowability agents ranged from 973 pounds to 1,229 pounds per minute.

“While there appeared to be differences in flow rate, the data suggested the differences weren’t consistently repeatable,” Johnston says. “Adding flow agents at levels that we studied provided little evidence of improved DDGS flowability. We’re looking deeper into the study to determine DDGS characteristics that might predict poor flow rates.”

For now, the study illustrates that DDGS moisture levels play an important role in determining the final product’s flowability. “Dryer is better for flow rates, but there is a danger that the nutritional quality will be reduced if the DDGS is dried too hard and fast,” Johnston says. The other concern, in terms of drying DDGS, surfaces during the summer when it can take on moisture during hot, humid days, thereby defeating the drying efforts.

The researchers’ goal in this is to prevent problems in commercial systems and to be able to explain differences in the flowability of DDGS products from different sources. “Then we can aid ethanol plants in improving the handling characteristics of the DDGS produced,” Johnston says.